Croque Madame

Name: Croque-Madame
Ingredients: Four ¼-inch thick slices french or italian sandwich bread; 2 tablespoons unsalted butter, plus more for buttering the bread; 1 tablespoon all-purpose flour; ¾ cup whole milk; Salt and freshly ground pepper; Freshly grated nutmeg; ¾ cup coarsely grated gruyère cheese; 2 tablespoons coarsely grated parmesan cheese; Dijon mustard; 6 ounces thinly sliced ham; 2 eggs